An analysis of data obtained on the H-2 immunogenicity studies with various tissue MLP has shown that spleen MLP will induce primary and secondary humoral and cell-mediated immune responses. Liver MLP has H-2 antigens but will induce only secondary H-2 immune responses, not primary. Both tissue MLP will induce killer cells in Marbrook cultures with primed spleen cells (secondary). Cytotoxic killer cells have been found in ascitic tumors of DBA/2 mice inoculated with small numbers of a compatible, progressively-growing tumor P815Y. By day 16, the in vivo P815Y tumor cells have modulated so that they are no longer sensitive to the in vivo generated killer cells. An improved radioimmunoassay for antibodies directed against cell surface antigens is being developed. Membrane fractions are bound covalently to filter paper discs. These discs act as the immuno-adsorbent to which antibody and radioactive reagents can be bound. Absolute quantification may be achieved in this system. BIBLIOGRAPHIC REFERENCES: Tax, A. and L.A. Manson. A radioimmunoassay for antibodies directed against surface membrane antigens using adhering cells. J. Immunol. Methods 11(3-4): 281-285, 1976. Manson, L.A. Intracellular localization and immunogenic capacities of phenotypic products of mouse histocompatibility antigens. In: Biomembranes, Vol. 8 (L.A. Manson, ed.), Plenum Publishing Corp., New York, 1976, pp. 47-87.